One of the major risks for a cable structure in the operating phase is fire, in particular of a vehicle, in particular in the vicinity of a cable securing zone, for example on a causeway.
A structural cable of such a work comprises taught metal reinforcements in order to transmit the forces required between its ends. The reinforcements are for example metal strands possibly contained in individuals sheathes made of plastic material. The harness of metal reinforcements is often surrounded by a collective sheath made of plastic material which provides the cable with aerodynamic properties, an aesthetic aspect and/or an anti-vandalism function.
WO 2007/093703 A2 describes a fire protection system comprising a mat comprised of a flexible insulating material that directly surrounds the reinforcement harness of the cable and which is contains in the collective sheath.
This system has for limitation not making it possible to effectively protect the cable in certain singular points where it interacts with other members of the structure. For example, if a deviator or a damper is applied against the cable, the presence of the flexible material of the mat prevents good communication of the forces and good operation of this member.
Singular points of this type are often present in the vicinity of the anchorings of the cables. This is the case for example for installing dampers of stay cables. Examples are described in EP 0 343 054 A1 and WO 2015/059413 A1.
These singular points are weak points of the fire protection.
In case of fire, the priority is to protect the reinforcement harness of the cable, even if peripheral equipment has to be replaced such as a damper or a deviator.
A difficulty is that the fire protection of singular points where peripheral equipment is connected must not decrease the correct operation thereof during the normal operation of the structure. For example, a damper or deviator collar must offer a sufficiently rigid point of support between the cable itself and the damping or deviator device. This constraint can contradict the implementation of good fire protection solutions, in particular those implementing a flexible mat surrounding the reinforcements of the cable. This mat passing through a collar would constitute a flexible interface, that decreases, for example, the performance of a cross damper anchored on this collar. Typically, the value of the transverse rigidity, in any direction orthogonal to the longitudinal axis of the cable, of the collar is never less than 106N/m (100 kgf/mm) and advantageously greater than 108N/m (10 tf/mm).
A purpose of this invention is to propose another method of protection capable of overcoming at least partially the difficulties hereinabove.